/*
 * Copyright 2020 the original author or authors.
 *
 * Licensed under the LGPL, Version 3.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at  http://www.gnu.org/licenses/lgpl-3.0.html
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.jn.sqlhelper.datasource.driver;


import com.jn.langx.util.ClassLoaders;
import com.jn.langx.util.Preconditions;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

/**
 * Simple implementation of the standard JDBC {@link javax.sql.DataSource} interface,
 * configuring the plain old JDBC {@link java.sql.DriverManager} via bean properties, and
 * returning a new {@link java.sql.Connection} from every {@code getConnection} call.
 *
 * <p><b>NOTE: This class is not an actual connection pool; it does not actually
 * pool Connections.</b> It just serves as simple replacement for a full-blown
 * connection pool, implementing the same standard interface, but creating new
 * Connections on every call.
 *
 * <p>Useful for test or standalone environments outside of a J2EE container, either
 * as a DataSource bean in a corresponding ApplicationContext or in conjunction with
 * a simple JNDI environment. Pool-assuming {@code Connection.close()} calls will
 * simply close the Connection, so any DataSource-aware persistence code should work.
 *
 * <p><b>NOTE: Within special class loading environments such as OSGi, this class
 * is effectively superseded by {@link SimpleDriverDataSource} due to general class
 * loading issues with the JDBC DriverManager that be resolved through direct Driver
 * usage (which is exactly what SimpleDriverDataSource does).</b>
 *
 * <p>In a J2EE container, it is recommended to use a JNDI DataSource provided by
 * the container. Such a DataSource can be exposed as a DataSource bean in a Spring
 * ApplicationContext via JndiObjectFactoryBean,
 * for seamless switching to and from a local DataSource bean like this class.
 * For tests, you can then either set up a mock JNDI environment through Spring's
 *  org.springframework.mock.jndi.SimpleNamingContextBuilder, or switch the
 * bean definition to a local DataSource (which is simpler and thus recommended).
 *
 * <p>If you need a "real" connection pool outside of a J2EE container, consider
 * <a href="https://commons.apache.org/proper/commons-dbcp">Apache Commons DBCP</a>
 * or <a href="https://sourceforge.net/projects/c3p0">C3P0</a>.
 * Commons DBCP's BasicDataSource and C3P0's ComboPooledDataSource are full
 * connection pool beans, supporting the same basic properties as this class
 * plus specific settings (such as minimal/maximal pool size etc).
 *
 * @see SimpleDriverDataSource
 * @since 3.4.0
 */
public class DriverManagerDataSource extends AbstractDriverBasedDataSource {

    /**
     * Constructor for bean-style configuration.
     */
    public DriverManagerDataSource() {
    }

    /**
     * Create a new DriverManagerDataSource with the given JDBC URL,
     * not specifying a username or password for JDBC access.
     * @param url the JDBC URL to use for accessing the DriverManager
     * @see java.sql.DriverManager#getConnection(String)
     */
    public DriverManagerDataSource(String url) {
        setUrl(url);
    }

    /**
     * Create a new DriverManagerDataSource with the given standard
     * DriverManager parameters.
     * @param url the JDBC URL to use for accessing the DriverManager
     * @param username the JDBC username to use for accessing the DriverManager
     * @param password the JDBC password to use for accessing the DriverManager
     * @see java.sql.DriverManager#getConnection(String, String, String)
     */
    public DriverManagerDataSource(String url, String username, String password) {
        setUrl(url);
        setUsername(username);
        setPassword(password);
    }

    /**
     * Create a new DriverManagerDataSource with the given JDBC URL,
     * not specifying a username or password for JDBC access.
     * @param url the JDBC URL to use for accessing the DriverManager
     * @param conProps JDBC connection properties
     * @see java.sql.DriverManager#getConnection(String)
     */
    public DriverManagerDataSource(String url, Properties conProps) {
        setUrl(url);
        setConnectionProperties(conProps);
    }


    /**
     * Set the JDBC driver class name. This driver will get initialized
     * on startup, registering itself with the JDK's DriverManager.
     * <p><b>NOTE: DriverManagerDataSource is primarily intended for accessing
     * <i>pre-registered</i> JDBC drivers.</b> If you need to register a new driver,
     * consider using {@link SimpleDriverDataSource} instead. Alternatively, consider
     * initializing the JDBC driver yourself before instantiating this DataSource.
     * The "driverClassName" property is mainly preserved for backwards compatibility,
     * as well as for migrating between Commons DBCP and this DataSource.
     * @see java.sql.DriverManager#registerDriver(java.sql.Driver)
     * @see SimpleDriverDataSource
     */
    public void setDriverClassName(String driverClassName) {
        Preconditions.checkNotEmpty(driverClassName, "Property 'driverClassName' must not be empty");
        String driverClassNameToUse = driverClassName.trim();
        try {
            Class.forName(driverClassNameToUse, true, ClassLoaders.getDefaultClassLoader());
        }
        catch (ClassNotFoundException ex) {
            throw new IllegalStateException("Could not load JDBC driver class [" + driverClassNameToUse + "]", ex);
        }
        if (logger.isInfoEnabled()) {
            logger.info("Loaded JDBC driver: " + driverClassNameToUse);
        }
    }


    @Override
    protected Connection getConnectionFromDriver(Properties props) throws SQLException {
        String url = getUrl();
        if (logger.isDebugEnabled()) {
            logger.debug("Creating new JDBC DriverManager Connection to [" + url + "]");
        }
        return getConnectionFromDriverManager(url, props);
    }

    /**
     * Getting a Connection using the nasty static from DriverManager is extracted
     * into a protected method to allow for easy unit testing.
     * @see java.sql.DriverManager#getConnection(String, java.util.Properties)
     */
    protected Connection getConnectionFromDriverManager(String url, Properties props) throws SQLException {
        return DriverManager.getConnection(url, props);
    }

}
